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CD22204 bảng dữ liệu(PDF) 4 Page - Intersil Corporation |
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CD22204 bảng dữ liệu(HTML) 4 Page - Intersil Corporation |
4 / 5 page 4 Outputs D1, D2, D4, D8 and EN Outputs D1, D2, D4, D8 are CMOS push-pull when enabled (EN high) and open circuited (high impedance) when disabled by pulling EN low. These digital outputs provide the hexadecimal code corresponding to the detected digit. The digital outputs become valid after a tone pair has been detected and they are then cleared when a valid pause is timed. The table below describes the hexadecimal codes. DV DV signals a detection by going high after a valid tone pair is sensed and decoded at the output pins D1, D2, D4, and D8. DV remains high until a valid pause occurs. N/C Pin This pin has no internal connection and should be left floating. DTMF Dialing Matrix Digital Inputs and Outputs All digital inputs and outputs of the DTMF receivers are represented by the schematic below. Only the “analog in” pin is different, and is described above. Care must be exercised not to exceed the voltage or current ratings on these pins as listed in the “maximum ratings” section. Input Filter The CD22204 will tolerate total input noise of a maximum of 12dB below the lowest amplitude tone. For most telephone applications, the combination of the high frequency attenuation of the telephone line and internal band limiting make special circuitry at the input to these receivers unnecessary. However, noise near the 56kHz internal sampling frequency will be aliased (folded back) into the audio spectrum, so if excessive noise is present above 28kHz, the simple RC filter shown below may be used to band limit the incoming signal. The cut off frequency is 3.9kHz. TABLE 1. OUTPUT CODES DIGIT D8D4D2D1 10001 20010 30011 40100 50101 60110 70111 81000 91001 01010 * 1011 #1100 A 1101 B 1110 C 1111 D 0000 XEN XEN CD22204 10 9 6 11 ATB XIN 3.579545MHz VDD XOUT 1M 10 11 6 XIN CONNECTED TO VDD UP TO 10 DEVICES CD22204 FIGURE 2. CRYSTAL OSCILLATOR COL 0 1209Hz COL 1 1336Hz COL 2 1477Hz COL 3 1633Hz ROW 0 697Hz ROW 1 770Hz ROW 2 852Hz ROW 3 941Hz NOTE: Column 3 is for special applications and is not normally used in telephone dialing. 1 2 3 A 4 5 6 B 7 8 9 C * 0 # D VDD VSS CMOS DIGITAL CIRCUITRY DIGITAL OUTPUT DIGITAL INPUT FIGURE 3. DIGITAL INPUTS AND OUTPUTS CD22204 33k Ω 0.0015 µF 270k Ω ANALOG IN NOISY SIGNAL FIGURE 4. FILTER FOR USE IN EXTREME HIGH FREQUENCY INPUT NOISE ENVIRONMENT CD22204 |
Số phần tương tự - CD22204_02 |
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Mô tả tương tự - CD22204_02 |
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